The present invention relates to the pressure molding of synthetic foam resin. Specifically, the top surface of the product is provided with a smooth finish by means of a cover belt that spans the individual rigid slats of the top conveyor.
Such a type of molding apparatus is shown in U.S. Pat. No. 3,824,057, issued to Andrew T. Kornyalk and Charles P. Tabler, July 16, 1974. The disclosure of this patent is incorporated herein by reference for background material as to the construction of the upper and lower rigid conveyors, and the operation of the molding apparatus in producing an endless product. One difficulty with this type of molding apparatus is that the upper belt engages the side dams and is clamped between the top and bottom rigid conveyors before the resin has fully expanded, so that with the usual width of 4 to 10 feet for such conveyors, there's a large unsupported central area of the top belt that tends to sag, because this belt is usually constructed of a resilient material, such as rubber or urethane. Thereafter, when the product expands and fills the pressure mold, a crease, wrinkle, or the like will be formed in the belt and consequently in the product.